The GRAINS module is a clone of the Eurorack module of the same name by Jan Willem from Ginkosynthese and as such can use the firmware that is accessible from that website.
However Mathias (aka VisuelleMusik) is a gifted software developer and dove straight in to develop his own firmwares specifically for the AE GRAINS module. These are now available from a dedicated Github repository: https://github.com/aemodular/GRAINS
If you have the GRAINS module, you should definitely check them out, they are really fun and interesting to play with. And looking at the code, who knows. You might want to develop your own firmware soon? If you do, please let Carsten (@admin) know!
